Various types of equipment, instruments, etc., used in hospitals, laboratories, and the like are sterilized for disinfection and killing bacteria and fungi. Plasma treatment is known as a sterilization treatment (see, for example, “3.3.1 Sterilization Experiment Using Low-Pressure Discharge Plasma” in NPL 1).
Plasma treatment is used not only for sterilization treatment but also for plasma dry-etching and plasma cleaning of the surface of articles to be treated, such as electronic parts, in the production of semiconductor devices.
Plasma dry-etching typically comprises applying high-frequency power to electrodes placed in a reaction chamber that is a vacuum vessel, plasmarizing a gas for generating plasma introduced in the reaction chamber, and etching a semiconductor wafer with high precision. Plasma cleaning removes metal oxides, organic substances, burrs, etc., deposited on or adhering to the surface of articles to be treated, such as electronic parts, to improve bonding or wettability of solder, thus enhancing bonding strength and improving adhesion to a sealing resin and wettability.
A method using a plasma treatment detection indicator comprising a color-changing layer that changes color in a plasma treatment atmosphere is known as a method for detecting the completion of these plasma treatments.
For example, PTL 1 discloses an ink composition for detecting plasma treatment comprising 1) at least one of anthraquinone colorants, azo colorants, and phthalocyanine colorants, and 2) at least one of binder resins, cationic surfactants, and extenders, wherein a plasma-generating gas used in the plasma treatment contains at least one of oxygen and nitrogen, and PTL 1 also discloses a plasma treatment detection indicator comprising a color-changing layer formed from the ink composition formed on a base material.
PTL 2 discloses an ink composition for detecting inert gas plasma treatment, comprising (1) at least one of anthraquinone colorants, azo colorants, and methine colorants and (2) at least one of binder resins, cationic surfactants, and extenders, the inert gas containing at least one selected from the group consisting of helium, neon, argon, krypton, and xenon, and PTL 2 also discloses a plasma treatment detection indicator comprising a color-changing layer formed from the ink composition formed on a base material.
These plasma treatment detection indicators are useful because they enable one to determine whether plasma treatment has been completed from the color change of the color-changing layer.
However, when a plasma-generating gas is not supplied or insufficient due to some defect in a plasma treatment device, overheating at up to about 170° C. caused unintentionally by application of AC voltage, pulse voltage, high-frequency waves, microwaves, etc., may change the color of the color-changing layer of these plasma treatment detection indicators. When this occurs, the completion of plasma treatment cannot be accurately determined. Thus, there is room for improvement in heat resistance of the color-changing layer so that overheating at up to about 170° C. as a result of a plasma-generating gas not being supplied or being insufficient does not change the color of the color-changing layer.
Thus, there is a demand for the development of a plasma treatment detection indicator comprising a color-changing layer that exhibits improved heat resistance so that the layer does not change color even when overheated at up to about 170° C. as a result of a plasma-generating gas not being supplied or being insufficient due to a defect in a plasma treatment device, and also an ink composition for detecting plasma treatment for forming the color-changing layer.